I am using big singles on everything. Twins can make the power but the PITA factor is very heavy with them, pulling turbo and pipes to get to a valve cover is just not cool. Parallel twins are not the answer at and dont even hit my radar, you want monster boost and that wont cut it, two stock turbos probably wont lite with 4 cylinders, they might but there will be lag. I can do one BIG single that will light faster then those two stock turbos and flow more then twice as much as two stock turbos.
Call Kai Zimmerman, 848-391-8341, he is selling one of my kits with a turbo that would put you in the 1550cfm range and ask him how it did on his truck.